Phenology and common garden and reciprocal transplant studies of Polymnia canadensis (Asteraceae), a monocarpic species of the North American Temperate Deciduous Forest

Polymnia canadensis, an herbaceous plant species of the North American Temperate Deciduous Forest heretofore reported as being perennial, is shown to be primarily monocarpic. In common garden experiments, the majority of plants grown from seeds or seedlings collected in Kentucky, Alabama, Virginia, Ohio, and Missouri were monocarpic, but some were dicarpic, tricarpic or polycarpic. Observations in natural populations of P. canadensis suggested that there is variation in the life history of this species throughout its geographic range. Anthesis date and height of plants at anthesis were significantly different between mesic and dry field sites in central Kentucky populations, but common garden and reciprocal transplant experiments showed that these were due mainly to environmental (and not to genetic) effects. The latter was also true for age of maturity and rate of change in plant height. Lack of significant site x source interaction for these characters indicated that plants did not differ in their plastic responses between sources at each site. Winter annual, biennial, triennial, and dicarpic and tricarpic perennial life histories occurred within populations in both common garden and reciprocal transplant experiments. In the latter experiments, most matured plants were either biennials (most common) or winter annuals (second most common), with the order reversed in the former experiments due to a more benign environment favoring earlier maturity. The extensive phenotypic plasticity displayed by P. canadensis for phenology and life history enables the species to inhabit a wide range of environments.